Electron discharge device



May 17, 1938. R. u. CLARK 20,727

ELECTRON DISCHARGE DEVICE 23 Original Filed Sept. 2, 1932 I NVEN TOR.

Reissued May 1 7,1938

UNITED STATES NT OFFICE.

PATE

ELECTRON niscmcn nnvrcn' Richard U. Clark, Fort Wayne, Ind.

Original No. 2,084,478, dated June 22, 1937, Serial No. 631,461,September 2, 1932. Application for reissue January 5, 1938; Serial No;183,562

16 Claims.

The present invention embodies in one tube or envelope the, elementsandparts necessary to Provide for the generation or by-passing ofconsiderable amounts of electric current, of an alternating or pulsatingnature, when properly excited by direct and/or alternating current thrusuitable connections to a wide variety of external circuits.

The present device is of the type known as an electron discharge orvapor electric tube. It employs a. single-or common cathode with aplurality of associated grids or anodes, or both, not more than two ofeither being shown in the appended drawing, but all being so arrangedthat 7 they may work independently of each other and withoutinterference but operating byvirtue' of the'electrons given oil by acommon cathode. The use of a single or common cathode as a source ofelectrons eiiects a very great saving in the amount of cathodeexcitation required for satisfactory operation, and due also to thecompact construction thus made possible the temperature rise within thetube, which helps to vaporize certain alkali metals such as caesium,rubidium, sodium, potassium, or the like, which are introduced into thetube in various amounts and combinations in order to obtain a very lowvoltage drop between anode and cathode within the tube, will be enhanceddue to the compact structure.

One of the objects of the present invention is to provide a novelconstruction of vapor electric tube employing a readily ionizableatmosphere, in combination 'with a common electron emitting means, aplurality of associated grids and anodes and means permitting a free andcontrolled flow of electrons from substantially the entire surface ofthe emitting means.

Another object of the invention is to provide a novel vapor electrictube having a common cathode or electron emitting means in combina- Ition with multiple grid and anode elements, and an apertured spacerencompassing the cathode or electron emitting means and so constructedand arranged as to permit a free and complete flow of electrons from theentire extent of, or surface area of, the electron emitting means;

A still further object of the present invention is to provide a noveltube construction having a common cathode or electron emitting means,multiple grids and anodes and a'spacer encompassing the cathode orelectron emitting means, all so shielded, constructed, arranged andcorrelated as to provide a novel combination of tube of the vaporelectric, multiple type. So faras I leads to the forming of arcs betweenam aware I am the first to conceive and disclose a tube whichaccomplishes the foregoing object. To completely understand the novelfunctions and constructions of the present device, it will be necessaryto consider in detail all, of the factors which aifect the operation oftubes of this general type, both favorably and unfavorably, and thesefactors are out 'ned in what follows.

.In an electronic tube of the ionized vapor type such as shown anddescribed here, and especially so in the types considered using alkalivapors to obtain anode to cathode voltage drops as low as 1% volts orless, there is very great danger of glow interference. betweenelectrodes and arcing back from anode toanode. Thereis also a chancethat arcing or current flow may take place from anode to grid betweentube sections desired to be kept separate in their electrical relationsto each other, but which must be of necessity closely spaced from eachother mechanically.

Thetendency for electrical leakage between parts within the tube islargely due to the fact that there is a considerable attraction or fieldset up by the glass walls of the tube and certain other parts, whichordinarily causes considerable spread of ionization within the tube.This often unwanted electrodes.

The grid or grids of the present device may carry alternating orpulsating current as well as the anodes, and said grids may often reachmaterially higher potential values than the anodes, although the reverseis more apt to be the case. In the event suflieient potential differencein the right polarity exists between a grid in one tube section and ananode in a totally diiferent section, there would exist a conditiontending to form an are between the two unless they were properlyshielded from each other. This is especially true if the grid isoperating at high temperature and the tendency would be very, pronouncedif caesium or the like is used within the tube.

The problem oi proper shielding within the tube becomes still morediificult when it isdesired to utilize, up to the total emission of thecathode, or nearly so, peak flows of current from one anode and thenanother as often as many hundred times a second. Such operation isdesired and is obtained in practice in the invention now beingoutlined.- This calls for complete .ionization of the space around theentire active surface of the cathode or electron emitting means in orderto overcome the space charge eflect; During such ionization, current canbe made to flow through certain desired paths which could not normallybe followed by electrons alone, and yet the ions which make possiblesuch diverse current paths must be kept within control in order that theentire cathode emission may be employed to carry full current between itand one anode.

Inthe present novel construction the efl'ects just outlined areaccomplished as is proven by the fact that when the tube is used as asingle wave rectifier alone the average anode current remains nearly thesame when either one anode alone, or many anodes in parallel areconnected to the source of current to be rectified.

In the drawing, Figs. 1, 2, and 3 are diagrammatic views in sideelevation of alternate forms of the novel tube construction.

The manner in which various currents are kept separate within the tubeand ionization is kept within control is best understood by aconsideration of the tube structure shown in Fig. I. In this figure, acommon cathode or electron emitting means is shown at it, within thetube l, heater excitation being supplied through the wire leads I, andII. This cathode 26, may be heated either as a filament or indirectly asshown, the latter method being preferred. Such indirect heating isstandard practice today and is therefore not described in detail.

The midportion of the cathode or common electron emitting means it isencircled by one or more mica, ceramic or othertypes of non-conductingwashers lll, having a diameter greater than the outside diameter of theanodes. This washer ll, acts as v stray arcs between adjacent tubesections. This insulating washer or spacer also acts to center the gridsi and I and may also anchor the plates in position as in Fig. 2. v

The hole at the centeroi the above mentioned spacers or bailles allowsjust sutflcient clearance around the cathode or electron emitting meansto permit a free flow of electrons and ions from one end of the cathodeto the'other. However, the various grids abutthe mica bailles in such away that no undesired leakage of glow or ionized vapor may take placebetween undesired sections. This is made possible by keeping the widthof grid mesh correct throughout the tube, and where extreme shielding isneeded a further precaution is taken by narrowing the openings betweengrid turns as the center of the cathode is approached. I a Where thegrid spacing is varied as just mentioned the current flow tends to takeplace through a longer path than might ordinarily be the case with anevenly spaced grid. It is well known that the grid in the present typeof tube has control up until struckwithin the tube. tion, in tubeshaving a very low anode to cathode drop, can be kept under controlbyproperly designing the grids and correctly shielding the plates of thetube, or anodes as they are generally known. For medium and high voltageoperation, complete shielding as with shields 23 and 24 at the end of Inthe present inventhe electrodes or elements, is desired. In tubesoperating at relatively high voltages a variation in grid spacing mighttend to cause arcing entirely through the largest mesh of the grid; Thiswould cause what is known as a hot spot and would quickly ruin thecathode. This is not so apt to be the case in tubes having an anode tocathode drop of 9 volts or below, especially where the variation of thegrid spacins is su lciently a screen or baifle to prevent the time thatthe arc is the path and density of the arc,especially In all presenttubes ,of the ionized vapor type where a single cathode or commonelectron emitting means is used in conjunction with more than one anode,the spacing between the various groups of grids and anodes, or anodes,if grids 5 are not used, is made as great as possible, as is also theirspacing from the cathode to prevent undesired interaction. In thepresent invention however all parts are bunched as close together aspossible in order to keep the anode .to cathode 10 drop as low aspossible, which cannot be done where wide spacing is employed.

Considering now in detail the structure of the tube shown in Fig. l, Iprovide a properly evacuated and sealed glass bulb i, with a number of 5lead wires passing through the glass stem of the tube, or press as it isknown, said press being numbered 21. Within this tube is a cathode whichmay be of the oxide coated type, of caesiated metal, or of any typeknown to the art which 20 is suitable for use with caesium and mercuryvapor or the like.

Surrounding the cathode 28 are the grids l and 8, the former beingconnected by the lead wire t,

,to the metal terminal cap 2 at the point I! where 25 the lead wirepasses through the glass bulb. The grid 6 is terminated by the lead wirell. Both of these grids abut against the mica or other insulating spaceror washer IIL the grid support rods being impressed somewhat into themica to 30 which they act as a support and centering member, while thewasher in turn helps to stay the grids. The grids should be pooremitters. a

Surrounding the grids just mentioned are'the v 5. These should beef 35-plates or .anodes l and material best suited for vapor electric devices.

Molybdenum and various high melting point =alloys containing apercentage of chromium have been found fairly satisfactory.

The carbonized type of plate or anode is also-desirable. Chro- 4o miumtitanium alloys and the like satisfactory as grid material. A low rateofemission in the presence of alkali vapors is desired-asgjin many casesthe grids run at very high' temperajtures. The general structure of the,grids and 45" plates may be very similar to that used for. the; innerscreen of the present screen grid tube and the present day plate oranode, except for the use of a variable grid mesh in some cases. Suchstructures are quite satisfactory for tubes up to several watts capacitywhere internal voltages between anode and cathode do not exceed eight ornine volts.

In Fig.1 an anode lead 9, and a heater lead l1,-

are shown as insulatedthrough the greater or entire portion of theirlength by the coverings 28 and i4, respectively. This insuiationsmaybein the form of glass tubing or some type of ceramic, either moulded orsprayed on the leads and properly treated to be gas free, and isespecially needed so or desirable in tubes where the voltage drop fromanode to cathode is of the order of two or three volts or less. 7 i

The remaining anode lead It from the. anode I,

. passes. thrdughthebase. I, as does the cathode 5 lead it, and theseand the various other leads previously mentioned are soldered to theterminal pins ii. The base 3, is of the usual moulded insulatingmaterial such as is in common use today but instead of the tube beingcemented directly to the base in the usual manner a ring of heatinsulating material l2, such as asbestos or the like is placed betweenthe tube and the base and can be cemented to both. This insulating ringl2, prevents the heat, from the tube from spreading to the base toorapidly during the warming up of the device, when same is first put intooperation, and thereby allows the bottom part of the .tube to heat uprapidly causing the alkali vapor I, which condenses to form a metal whencool, to increase the vapor pressure within the tube, which makes itpossible to obtain the low voltage drop desired between anode andcathode. The leads mentioned above except for 22, are taken out o! thebulb through the glass press or seal 21.

The type of tube shown in Fig.' 2 is intended for use as a rectifier ofalternating current or a by-pass for alternating or pulsating current.The general structure of the tube shown in Fig. l is maintained exceptthat the grids are omitted and the anodes are stayed to the insulatingspacer II, by the feet II. A large number of plates or anodes may beused around a single or common cathode in a tube of this nature when thesame is intended to be used as a by-pass device, and in some such casesthe shield spacers or washers ill,

-may be cut down materially in size. One particular use intended forthis type of tube is as a multiple by-pass unit for radio receiverswhere it has been used by the present inventor to .bypass all pointssumciently above ground potential to conform with the internal tubedrop. Points of .unconforming potential are by-passed thru anodebleeders which add little resistance between anodes and by-pass points.

When used as a rectifier, the tube shown in Fig. 2 functions aseconomically as the oscillator tube shown in Fig. 1 the entire cathodefurnishing electrons forv each half of the rectified wave. By making useof this arrangement and type of construction nearly 50% is saved incathode. excitation. Where large amounts of energy or peculiar voltagewave forms are encountered and must be rectified, it may be founddesirable to heat shield part of the cathode somewhat after the mannershown at 25, in Fig. 3.

Where such a shield fits tightly through the hole cathode 25 as in Fig.3, the grid spacing can be.

kept constant under all conditions. Also the cathode operation becomesmore efilcient and the.

grids heatlss; This type of tube has an advantage over that shown inFig. 1 for high output or capacity. The grids in both Fig. 1 and Fig. 3and their cathodes are closed in by the insulating shields 23 and 24,which may be recessed to help center the cathodes and shields. Theseheat shields are welded to the cathode so that the two becomeelectrically common. This is designated by thickening the heat shieldat'the point'where it ouches the cathode top in Fig. 3. In Figs. 1, 2,and 3, the heater coil is shown by dotted lines inside the cathode.

The tubes shown in Fig. 1 and Fig. 3 may both so generated within thetube may be transformed and rectified at various desired voltages withinthe same tube by application to the tube grids.

Having described the outstanding points of the present invention. what Iand wish to protect is as follows: I

v 1. A vapor electric tube having an ionizable atmosphere, two adjacentgrids, two plates, and a common electron emitting cathode, an insulatingspacer abutting the adjacent grids and having an aperture surroundingthe cathode, said aperture havingsufilcient clearance thereabout toallow the passage of electrons and ions from one end of the cathode tothe other whenever either grid prevents emission of electrons to itsrespective plate.

2. A vapor electric tube having an ionizable atmosphere, two adjacentgrids, two plates, and a common electron emitting cathode, an insulatingspacer abutting the adjacent grids and having an aperture surroundingthe cathode, said aperture having sufiic ent clearance thereabout toallow the passage therethrough o! the electrons and ions from one end ofthe cathode to the other whenever the charge on either grid preventsemission oi electrons from the cathode, to its revents emission ofelectrons to itsrespective plate and heat insulation between the lead-inend of said tube and the base of the tube.

4. A vapor electric tube comprising an evacuated bulb containing anionizable atmosphere, an electron emitting cathode, two; grids, twoplates, and an apertured disk-like non-conducting separating spacerhaving a diameter not less than the diameter of the plates, said gridsenclosing the cathode and controlling the path of emission therefrom andpositioned so as to abut the spacer and thereby shield one portion ofthe cathode from its remaining portion, so as to prevent thesimultaneous external fiow of electrons and ions from both ends of thecathode except through the aperture in the spacer, said aperture beingof sufiicient size and displacement to allow for the free fiow of saidcathodes emission therethrough as required in the operation of thedevice.

5. A vapor electric tube comprising an evacuated bulb containing analkali metal and an ionizable gas, an electron emitting cathode, twogrids, two anodes, and an apertured disk-like nonconducting separatingspacer having a diameter not less than -the diameterot said anodes, saidgrids enclosing the cathode and controlling the path of emissiontherefrom and positioned to abut the spacer and thereby shield oneportion of the cathode from its remaining portion, .50 as to prevent thesimultaneus flow externally of electrons and ions from both ends of thecathode except through the aperture in the spacer, said aperture beingof sufiicient size and displacement to allow for the free flow of saidcathodes emission therethrough as required in the operation of thedevice. 7

. 6. A vapor electric tube oi. the type employing two grids, two plates,a common electron emitting heat shielded cathode; an insulating spacerabutting the adjacent grids and having an aperture surrounding thecathode, the aperture having sufficient clearance thereabout to permitthe passage of the electrons and ions from one end of thecathodetotheotherthroughsaidapertureto supply emission from the entirecathode to the tube section controlling ionisation.

7. In a vapor electric tube having an ionisable atmosphere, a pluralityof grids and cooperating plates, an insulating spacer mountedintermediate said grids, a common cathode provided with a shield forminga part of the cathode mounted in said spacer and p ded with openings forbypassing the. flow of electrons and ions and for directing emission 60msubstantially the entire surface of the common cathode to one plate at atime.

8. A vapor electric .tube having a plurality of grids and plates, acommon electron emitting means, an insulating spacer adjacent the gridsprovided with an opening and a shield for the emitting means mounted insaid opening, said shield being provided with openings to permit thepassage of electrons and ions from one end of the emitting means to theother and to supply emission to either plate. Y

9. A vapor electric tube of the type employing two grids, two plates,and a common electron emitting cathode, an insulating spacer adapted tobe mounted intermediate said grids and having an aperture for thereception of said cathode, said aperture being of a size anddisplacement sufiicient to by-pass the flow of electrons and ions fromone portion of the cathode to the other and direct emission fromsubstantially the entire surface of the common cathode to one plate at atime.

10. In a vaporelectric tube of the type employing a readily ionizableatmosphere, two grids, two plates, and a common electron emittingcathode, an insulating spacer adapted to be mounted intermediate saidgrids and having an aperture for the reception of said cathode, saidaperture being 'of a size and displacement sufflcient to by-pass theflow of electrons and ions from one portion of the cathode to the otherand direct emission from substantially the entire surface of the commoncathode to one plate at a time.

11. A vapor electric tube of the type employing multiple grids andplates and a common electron emitting means, an insulating spaceradapted to be mounted intermediate adjacent grids and having an aperturefor the reception of the electron emitting means, said aperture being ofa size and displacement suflicient to by-pass the flow of electrons andions from one portion of the electron emitting means to the other anddirect emission from substantially the entire surface of the commonelectron emitting means to one plate at a time.

12. A vapor electric tube having a readily ionizable atmospherecomprising a plurality of of a size and displacement sufficient toby-pass' the flow of electrons and ions from one portion of the cathodeto the other and direct emission from substantially the entire surfaceof the common cathode to one plate at a time.

13. A vapor electric tube of the type employing multiple grids andplates and a common electron emitting means, and means forming apassageway for by-passing the flow of electrons and ions and forpreventing stray ironization between tube sections so as to directemission from substantially the entire surface of the common electronemitting means to one plate at a time.

14. A vapor electric tube of the type employing multiple grids andplates and a common electron emitting means, and means within the tubeand positioned intermediate the grids and plates forming a passagewayfor by-passing the flow of electrons and ions and for preventing strayionization between tube sections so as to direct emission fromsubstantially the entire surface of the common electron emitting meansto one plate at a time.

15. A vapor electric tube of the type employing multiple grids andplates and a common electron emitting means, means mounted within thetube and forming a passageway for by-passing the flow of electrons andions from one end of the electron emitting means to the other to makeavailable and confine the entire cathodes emission to each plate at suchtimes as its coop-- crating grid initiates ionization.

16. 'A vapor electric tube having a plurality of grids and plates, acommon electron emitting means, a shield for the emitting. meansprovided with openings to permit the L a: of electrons and ions alongthe entire surface of the emitting means so as to supplyemission to oneplate at a time, and means to prevent stray ionization between the tubesections.

n RICHARD U. CLARK.

